Well as someone who really does have nightmare about plastic mags (Thermold
) I got a few of the PMags.
I have left two loaded in the Suburban to see if heat will screw with them.
I drove over one yesterday with a B6 Suburban - and while it cracked (on the spine) - only one round of Mk262 popped out -- and the mag loaded and fired fine. I reloaded it 4 more times and shot some drills with it and had no problems.
I figure it has to be possible to make a good poly mag -- since my Glock and our Sig552's work well with poly mags